Seeinstructions): Adherence with immunosuppressive medication is an essential component of successful solid organ transplantation. The recent advent of increasingly effective and potent drugs to prevent allograft rejection has generated new interest in medication adherence. While nonadherence certainly leads to adverse outcomes, that very observation highlights our lack of detailed information about the quality and quantity of medication adherence required for optimal results. This research proposal will prospectively apply electronic medication monitor technology (Medical Events Monitoring System - MEMS) to capture a quantitative chronology of immunosuppressive medication adherence and begin addressing at least three basic questions. Can an intervention focused on the least compliant patients improve or stabilize medication compliance? Aim 1- will complete enrollment and followup for a randomized study of an intensive intervention to improve medication-taking behavior. High-risk participants are prospectively identified by their early posttransplant noncompliance and stratified by their immunosuppressive drug regimen. Their behavior is tracked electronically during a two-year intensive intervention period with discrete clinical end-points including, acute or chronic rejection and graft loss. Can pretransplant adherence coupled with personality characteristics reliably predict post-transplant medication adherence and likely allograft outcomes? Aim 2- will complete a prospective study of 100 patients. Their medication adherence will be quantified before and after transplant. Those data together with specific personality attributes and demographic characteristics will then be combined to improve the prediction of each individual patient's post-transplant adherence behavior and outcome. What role does medication adherence play in later posttransplant morbidity? Aim 3- will critically examine late medical morbidity, specifically skin cancer, in a group of 137 renal transplant recipients who are 10 years posttransplant and now increasingly present with cancers. Their medication compliance was precisely quantitated during their first 4 years post-transplant and now appears positively associated with their development of cancer. Answers to each of these questions will permit us to substantially improve long-term renal transplant outcomes. RELEVANCE (Seeinstructions): There are fundamental questions about our ability to either predict or alter an individual patient's medication taking behavior. Now newer questions arise concerning the potential for adverse consequences in patients with excellent or over-adherence with immunosuppressive drugs. This research, by careful measurement of medication adherence and prospective followup of renal transplant patients will try to answer such questions.